This volume contains the refereed papers presented at the International Workshop on Software Encryption Algorithms, held at Cambridge University, U.K. in December 1993.The collection of papers by representatives of all relevant research centers gives a thorough state-of-the-art report on all theoretical aspects of encryption algorithms and takes into account the new demands from new applications, as for example from the data-intensive multimedia applications. The 26 papers are organized in sections on block ciphers, stream ciphers, software performance, cryptanalysis, hash functions and hybrid ciphers, and randomness and nonlinearity.